In the United States, nearly four million infants are born each year, with a large fraction (including more than 500,000 pre-term deliveries) at risk for under-developed feeding performance levels at the time of hospital discharge, and for medically significant feeding problems after discharge. Assessment and analysis of feeding performance as an infant approaches readiness for hospital discharge is widely recognized as very important for discharge timing, and as one prospective indicator of medical and developmental progress (or problems) in the weeks after discharge, as well as in later infancy. Yet, in common practice, infant feeding assessment is most often highly subjective, with substantial variability of practices across neonatal nurseries. The lack of an objective and quantitative standard for feeding assessment is a particular concern for “challenged infants”, including premature infants, i.e., those born before completion of the 37th gestational week. Feeding in infants born very prematurely (at 34 weeks gestational age [GA] and earlier) is monitored carefully at early stages, during which feeding therapy is often administered to promote safe acquisition of rudimentary feeding skills. However, feeding performance of the same infants often receives much less attention as hospital discharge nears despite the fact that their feeding skill level at this time, on average, is significantly weaker than that of infants delivered at term. The consequences of inadequate screening bear most heavily on those pre-term infants whose feeding skills fall below, or well below their group average. Thus, a physician may discharge some infants not knowing they may be incapable of independent oral feeding, and marginal feeders may be discharged without appropriate notation of feeding status in the discharge plan. Infant feeding problems often carry forward after discharge, contributing in part to high hospital readmission rates for premature infants (20-25% vs. 1-3% for full-term infants), and contributing to high usage rates for other medical services (including acute care visits, non-routine physician visits, and feeding therapy) related directly or indirectly to poor feeding performance. It is likely that the associated economic, social and familial burdens can be reduced by systematic and standardized evaluation of feeding performance before and after hospital discharge in order to better identify of those infants at greatest risk for adverse outcomes, who would benefit from preventive or ameliorative interventions.
Current techniques for assessing feeding performance of full-term infants with uneventful deliveries are cursory, non-quantitative and subjective. For example, a typical assessment involves (1) “the finger test” where a finger is inserted into the infant's mouth to determine if the infant produces an adequate amount of negative sucking pressure, (2) observing whether the infant orients to a nipple stroked against the perioral region, and (3) observing that a salient amount of milk or formula is ingested (but with no standard guideline for an acceptable amount). Such techniques do not provide a quantitative or objective assessment of the infant's feeding performance. In fact, two people performing the same observations on the same infant may reach different conclusions about the infant's feeding ability.
With notable exceptions, most infants born prematurely receive feeding evaluations hardly more systematic than that described above when they approach readiness for hospital discharge; that is, after the primary medical comorbidities of pre-term delivery (e.g., apnea of prematurity) have been resolved or ameliorated, and after a few days of observation, referred to as the “margin of safety,” beginning when the infant first meets criteria for physiological maturity. Nevertheless, some infants do receive much greater attention to their feeding status during the latter portion of the hospital stay. These include those not feeding independently according to the cursory assessment, and early pre-term infants who were not candidates for, or were not responsive to, prior efforts to promote feeding skill acquisition. In these cases, services of a specialist (e.g., a speech-language pathologist, or an occupational therapist or nurse with appropriate training) are often ordered, which may include administration of standard diagnostic tests (e.g., a fluorographic swallow study to detect morphological anomalies or the oropharynx), and a thorough evaluation of feeding performance. Unfortunately, however, such feeding assessment methods have not been standardized, and a mosaic of practices and procedures are currently employed. One example is the Neonatal Oral Motor Assessment Scales, a lengthy protocol involving completion of numerous tests, and visual evaluation of sucking rhythmicity and of coordination between sucking, swallowing and breathing movements. NOMAS must be performed by trained, certified raters, and inter-rater reliability remains an issue. Another protocol employs instrumentation to record negative sucking pressure, and expression pressure (i.e., squeezing pressure applied to the nipple) during bottle-feeding tests. From these records, the infant receives a “sucking maturity” rating according to a five-point scale. Here, objective records are provided, but the assessment involves visual inspection, selection of record segments deemed representative of overall feeding performance, and categorical assignments based on the judgment of a trained rater. Shortcomings of these and related assessments include (1) limited extent of current clinical use, (2) biases related to a significant measure of rater subjectivity, (3) lengthy test duration, (4) expense associated with professional assessors.
Notwithstanding conventional practices for assessing infant feeding performance, devices for quantitatively measuring certain parameters related to infant feeding are known. For example, U.S. Pat. No. 3,895,533 (Steier) discloses a device resembling a baby bottle for measuring the negative sucking pressure of an infant to determine if the baby has a relatively poor sucking ability. U.S. Pat. No. 4,232,687 (Anderson-Shanklin) discloses a feeding nipple apparatus for measuring the negative sucking pressure and expression pressure that an infant exerts on a test nipple. The purported purpose of this apparatus is to measure an infant's (in particular a premature infant's) capacity to bottle feed in order to mitigate the risk of regurgitation or milk aspiration. Another device is shown in U.S. Pat. No. 6,033,367 (Goldfield) which discloses a system for diagnosing and/or monitoring sucking, swallowing, and breathing competence of an impaired neonate or postoperative infant. The system of Goldfield involves sensors for measuring negative sucking pressure and breathing rate as well as an automated valve and computerized feedback loop to control the amount of fluid flowing through a feeding nipple to an infant as a function of the infant's negative sucking pressure and breathing rate.
Each of the aforementioned publications discloses a means for measuring particular factors that are related to an infant's feeding performance, but most, however, link a measurement device with specific protocols focused on improving feeding performance (particularly in relation to initial acquisition of feeding skills), and none disclose a quantitative method suitable for broad-based diagnostic screening; that is, they do not disclose a method of evaluating the feeding performance of an infant that involves comparing feeding performance data of a single infant to an objective standard, such as a metric derived from a population-based sample of infants.
The clinical research literature contains a number of studies in which infant feeding performance is characterized and analyzed. Examples of feeding parameters analyzed include the number of sucks in a test session, duration of sucking bursts, and relationship between sucking and breathing rhythms. These studies, however, generally treat a small number of specific parameters of interest, and emphasize statistical evaluation of differences in feeding performance between groups of selected interest, of effects of a clinical treatment or intervention on feeding performance, or of changes in feeding performance as a function of time, maturation or experience. Such research has not focused on individual subject differences in feeding performance except as relevant to subject variance for specific statistical analyses, or in relation to subject differences in response to specific experimental variables. Not provided, then, are methods for scaling feeding performance of individual infants in relation to population-based norms, or methods suitable for a broad-based screening instruments for assess an infant's risk for adverse outcomes related directly or indirectly to poor feeding performance.
Thus, there remains a need for a quantitative and objective means for assessing the feeding performance of an infant, and for scaling said performance in relation to population-based norms and, ideally, to risk for adverse outcomes. The present invention satisfies this need among others.